being 1-5-2%). They are very rich in carbon (2-5%), which occurs entirely
in the graphitic state in ordinary grey cast-irons, and partly combined in the
lighter ones. They contain also small quantities of manganese (about i%) and
sometimes sulphur (0-01-0-1%) and phosphorus (0-05-1-8%). They serve in
general for foundry purposes and those with little phosphorus for refining.
White cast-irons have a shining, white colour tending to grey, a crystalline,
granular and, sometimes, radiating fibrous structure ; they melt at about 1100°
and have the specific gravity 7-4-7-5. They contain 2-3-5% of carbon, largely
combined, and only small quantities of silicon (0-5-1%), but they are very rich
in manganese (1-5%), and sometimes contain considerable proportions of sul-
phur (0-1-0-25%) and phosphorus (more than 3%). They are usually employed
The products containing more than 5 % of manganese are : Spiegeleisen (5-30 %
Mn, 0-2-1-2% Si and 4-5% C), Silico-Spiegel (20% Mn, 10-12% or even more Si),
and Ferro-manganese (30-85% Mn and up to 7-5% C).
Malleable iron represents the product of the refining of cast-iron, contains
less than 2 % of carbon and, according to its carbon content, to its uses, and to
its hardness, elasticity, strength, etc., is subdivided into : soft iron (soft wrought-
iron or mild steel, according to the mode of preparation), which is very ductile
and malleable and contains less than 0-3-0-5% of carbon ; and steel (cementa-
tion or blister steel, crucible steel, cast steel, etc.), which has larger amounts of
carbon (more than 0-3-0-5%) and is ductile and malleable, but very hard, elastic
and resistant and capable of being hardened. Steels with more than 1-5%
of carbon begin to lose their malleability and become brittle.
Small quantities of silicon increase the hardness of malleable iron but dimin-
ish its malleability (a good malleable iron should not contain more than o-i-
0-2%). Most harmful for malleable iron are phosphorus, which even in small
quantities (0-1%) renders it cold short, and sulphur, which renders it red short
even in the proportion of 0-05-0-1%. Manganese diminishes the harmful
effects of sulphur and hence improves the quality of iron and steels. Injuri-
ous actions are also exerted by arsenic, tin, antimony, copper (beyond 0-4%),
The following table gives the compositions of various commercial types of
soft iron and steel.
Compositions of Various Iron and Steels (percentages)
Swedish iron .
Wrought steel .
Ingot iron for construc-
Ingot steel for rails
Martin steel for castings
Crucible tool steel .
of potassium iodide may be